Tesla shares hit their highest in nearly a year Monday after CEO Elon Musk said the electric-vehicle maker was testing its robotaxis without safety monitors in the front passenger seat.

While much of Tesla's $1.53 trillion valuation — the highest of any automaker globally — is tied to investor optimism around its self-driving technology and humanoid robot ambitions, the bulk of its revenue and profit still comes from selling electric vehicles.

Shares of the company rose as much as 4.9%, hitting $481.37, their highest in nearly a year.

The stock had hit a record high of $488.54 on December 18 last year on hopes that the Trump administration would ease regulatory hurdles for self-driving cars.

Tesla launched a limited robotaxi service in Austin, Texas, in June using modified Model Y vehicles equipped with Full Self-Driving. Early operations were geo-fenced and included a human "safety monitor" in the passenger seat.

"Testing is underway with no occupants in the car," Musk said in an X post on Sunday.

Investors and analysts are betting that Tesla will intensify testing and rapidly deploy driverless taxis as it prepares to launch its Cybercab model next year.

"The news Tesla is testing robotaxis without the safety monitors is in line with our expectations that the company is making progress in its testing, in line with management's statements during the third quarter earnings call," said Seth Goldstein, senior equity analyst at Morningstar.

"The market is cheering the progress, sending shares higher today."

Tesla has long touted its robotaxi and self-driving taxi plans, though regulatory obstacles and technical setbacks have repeatedly slowed their progress.

Alphabet unit Waymo leads with more than 2,500 commercial robotaxis across major U.S. cities, as of November. CNBC reported last week that Waymo has been operating about 450,000 paid rides per week.